Can dial extension one way but not the other

I have two extensions set up 004 & 005.
I can ring internally from 005 to 004 but when i try the other way round the softphone gives the following message "Error returned: Service unavailable" then "call has disconnected".

Hi Rob
I've just tried turning off the separate PC firewalls (firewall and filtering already set to off on the Router) and also setting the SIP port to 5060 on the soft phone settings but that doesn't make any difference (5070 is the default on the soft phone that I'm using).

I'm using a soft phone called "Express talk" it's the only free one that i can find that will ring internal extensions (while i try out 3CX), I suppose it could be that but i doubt it.

I've a similar problem. I tried to change to 5061"Local sip port to listen on", but nothing todo.

I've 3 PC with 3 external number all firewalls disabled. I'm using Express talk session for each pc. The external number are 102,103,101. I can comunicate only between 103->101 (only if 103 is caller) all other combinations the phone caller ring but 3cx do not pass the call to the extension. On status I see the message:
[CM103002] Call(22): Incoming call from 101 (Ext.101) to sip:103@192.168.1.100:5060

I didn't understand a thing.... On Express Talk the parameter "Local sip port to listen on:" under Network, what mean ? If I've 3 express talk instance on my network, this parameter is equal for all ?

I appear to have solved my extension dialing problem, which I think was basically down to me being too much of a novice to be doing it all myself.

The reason why it wouldn't work both ways was because i'd got a box ticked on all the soft phones that said " Use static IP address and static mapped ports". if I un-tick the box on all the soft phones except the phone on the 3CX server PC then it all seems to work OK.

Fala70 don't forget, as I did, that whatever changes you make to the SIP ports etc on the soft phones you must also make on the 3CX server.